johnny2

Does anyone know where P O Ackley got his forumla to
base his cartridges on? I have one I am working on here
and would like to know the forumula..

rem250

P O Ackley used existing cases, just improved onthem like sharper shoulder angles
to make them highercapacity

Pavomesa

Many of Ackley's creations really weren't entirelyhis ideas...rather someone would contact him and pay P.O. to build such and such. Ackley was first a gunsmith and many of the cartridges with his name on them are really crap that someone else dreamed up and paid him to make. Ackley was never bashful about telling his readers when a cartridge design was garbage either. (Even if it did have his name on it.) Conversely when Ackley says a design is a good one, you can take that to the bank.

johnny2

it just seems to me that he much have had some way of figureing
out how much of an angle to use in relation to how much extra
powder he could get in the case..He must have left some notes
or something,somewhere...
I have another wild cat idea and wish i knew his forumla...

Pavomesa

I don't think he had a formula. He often used what he called "minimum body taper" meaning the minimum taper you could use and still extract a fired case. And I think he had a couple of pet shoulder angles.

Suggest you acquire his books, "Handbook for Shooters & Reloaders." Especially volume 1.

Mr. Ackley was a purist about cartridge EFFICIENCY. He hated powder burning, barrel eating cartridge designs and basically thought they were a hell of a waste. He coined the phrase "overbore capacity" and I think this was his "formula" if you will. Bore capacity simply means the amount of powder you can use in each particular bore diameters and get your money's worth. For every diameter you will reach a point of rapidly diminishing returns, i.e. lots of powder in and not much velocity out. Example - In the 30 caliber bore this occurrs around 60 grains of powder. The smaller the bore, the smaller the charge before you reach this point.

I guess what I'm thinking is Ackely seemed to worry more about bore capacity than the particular case or shape of the case. The cartridge case is essentially nothing but a container. It's the volume of the container that matters. (That and the cartridge feeding and extracting.)

Or such was my take on Mr. Ackley's works.

SwampCollie

The angle is generally 40 degrees. He wrote a book with two volumes, which I suspect you have already reviewed.

falcon

Some of the Ackley Improved cartridges work very well. Others do not. Used to own identical pre-64 model 70 Winchester rifles, one in .30-06 and the other in .30-06 AI. The Ackley Improved chambered one just used more powder to equal the velocity of the .30-06. Still have the rifle chambered for .30-06. TheAI one went away.

skb2706

I believe through exhaustive testing he determined that 40 degrees was about as much as brass could be formed sharply for ashoulder and not split on fire forming. The minimum body taper again was determined by how minimum it could be and not get stuck in the chamber. Both of my current AIs have a body taper of .004" from head to shoulder.

Pavomesa

The MBT and a 40' shoulder is going to provide the most case capacity for a given case...but I have to question is getting the last kernel of powder in a case all there is to it? There are some really, really fantastic cartridges that don't have either feature. And doing the AI routine on them has helped very little if any. And I'm not talking about cartridges so badly overbore capacity already that nothing would help them.

I'm just thinking aloud. When is enough enough? When is something JUST RIGHT?[:-]

skb2706

There are plenty of modern day shooters that will argue that nearly any cartridge based on .308 brass is as effective as it can be with regard to body taper, shoulder angle and powder capacity for caliber. I am in that camp....I believe that PO Ackley was also in that camp.

Trying to get the most, from least did not always yield the best.